refactor: sort all top-level imports

[agilgur5]

Summary

Sort imports by external deps first, then local/internal deps next (AKA absolute imports first, then relative imports)

Details

• basically, general format is:

  import x from "external-dep"
  
  import y from "./internal-dep"

  • so external deps, new line, then internal/local deps
  • with some further sorting within there, like trying to keep Node built-ins (e.g. path) at the top half of externals, then core deps like typescript, then any other external deps
    • and similar for internal deps -- core internals at the top half of internals, then any other internal deps
    • just to keep things consistent between files -- makes the top easier to read through when it's similar between files
    • also makes it easier for contributors to understand where to put imports, as there's a sorting already there

• this is how I generally sort my imports and how I wrote most of the unit test suite's imports as well (c.f. test: add initial unit test suite #321)

• there is automation for this that we should probably add once TSLint is replaced here; some previous art:

  • https://github.com/trivago/prettier-plugin-sort-imports
  • https://github.com/lydell/eslint-plugin-simple-import-sort/
  • Older:
    • https://github.com/renke/import-sort/tree/master/packages/import-sort-style-module
    • https://github.com/mcdougal/js-isort
    • inspired by Python's isort ofc